sparklines in Clojure

spark.clj

(defn normalize
  "Returns a sequence of normalized (0 to 1.0) numbers in coll."
  [coll]
  (let [min (apply min coll)
        r (- (apply max coll) min)]
    (map #(/ (- % min) r) coll)))

(defn spark
  "Returns UTF-8 sparkline string for numbers."
  [nums]
  (let [blocks "▁▂▃▄▅▆▇"
        scale (-> blocks count dec)]
    (->> nums
         normalize
         (map #(nth blocks (-> (* scale %) double Math/round)))
         (apply str))))